1. Field of the Invention
The present invention relates to a process cartridge and an image forming apparatus.
2. Description of the Related Art
In recent years, colorization has been extensively applied to image forming apparatuses such as copiers, printers, facsimile machines, and multifunction products (MFPs) with a plurality of functions. Particularly, a tandem type that has a plurality of image bearing members excels in speed and is becoming a mainstream. In the tandem type image forming apparatus, an apparatus used by arranging four process cartridges in parallel is known. Because miniaturization of the apparatus is an element that directly leads to customers' convenience, the process cartridges are generally arranged closely as possible, or a space between other units are narrowed.
On the other hand, to meet demands for energy savings, a method of lowering temperature required for a heat-fixing unit by lowering a toner melting temperature is generally used to reduce power consumption.
Accordingly, these make it difficult to remove heat caused by self-heating of the process cartridge, due to a small number of spaces. Further, the toner apt to melt due to the self-heating is susceptible to damage.
The self-heating of the process cartridge is largely caused by frictional heat in a developing roller unit due to sliding and friction with a restricting blade, and sliding frictional heat in a drive transmission. Because the drive transmission is generally gathered to one side of the cartridge, the generation of heat in the drive transmission causes by temperature deviation.
To reduce such a problem, Japanese Patent Application Laid-Open No. 2005-258316 discloses a conventional technology for ventilation within a space where gears are stored, thereby suppressing a temperature rise within the process cartridge. Japanese Patent Application Laid-Open No. 2005-173226 discloses another conventional technology for ventilation in which an air duct is provided in a hollow portion formed by a developer restricting member and a developing frame body.
However, the former conventional technology increases the size of the apparatus. With the latter conventional technology, the process cartridge is formed in a substantially rectangular shape and ventilated in a longitudinal direction to be cooled. This causes a rise in the temperature at a downstream side, resulting in temperature deviation.